Rotary electric machines such as a generator or an electric motor usually have members such as a stator and a rotor. Particularly in an air-cooled turbine generator, cooling air is supplied to a circulating airflow path in the generator so that the stator, the rotor, and the like are cooled. The stator of this air-cooled turbine generator is usually formed of a core and a coil wound around the core, on which treatment for preventing partial discharge is performed. However, the partial discharge may occur due to various factors such as deterioration over time of winding insulation or a partial discharge inhibitor. Then, when the partial discharge occurs in the generator in which humid air circulates in the same manner as outside air, ozone (O3), nitrogen oxides (NOx), nitric acid, and the like are produced and spread in the generator along with the air circulation. As a result, metal members (for example, bolts and aluminum fins) in the generator may be corroded, or organic materials may be deteriorated. Therefore, it is necessary to reduce ozone, nitric acid, and the like.
Similarly, in large electric motors as well, ozone, nitrogen oxides, nitric acid, and the like may be produced in the circulating airflow path due to the partial discharge caused by high electric fields. Therefore, in large electric motors as well, it is necessary to reduce ozone, nitric acid, and the like from the viewpoint of suppressing corrosion of metal members and improving the working environment.
There are several methods proposed for reducing ozone, nitrogen oxides, nitric acid, and the like.
For instance, Patent Document 1 proposes a method of disposing a filter device including a removing agent for removing at least one of ozone and nitric acid gas in the circulating airflow path of a rotary electric machine. In this method, activated carbon (adsorbent) is used as the removing agent for ozone, and a chemical adsorbent is used as the removing agent for nitric acid gas, and hence concentrations of ozone and nitric acid gas are reduced by the respective adsorbents.
In addition, Patent Document 2 proposes a method involving reacting difficult to adsorb NOx (NO and NO2) with ozone so as to produce nitric acid, adsorbing and removing nitric acid using a silicon adsorbent, and decomposing and removing residual ozone using an ozone decomposition catalyst.